Journal of Physical Chemistry A, Vol.107, No.48, 10288-10291, 2003
Kinetics of CCN radical reactions with a series of normal alkanes
The reactions of CCN((X) over tilde (2)Pi(i)) radicals with normal alkanes have been studied at about 10 Torr total pressure and room temperature using the pulse laser photolysis/laser-induced fluorescence technique. CCN ((X) over tilde (2)Pi(i)) radicals are generated by the fourth harmonic of a Nd:YAG laser photolysis of Cl3CCN at 266 nm. The relative concentration of CCN ((X) over tilde (2)Pi(i)) radicals was monitored in the (0-0) band of the CCN ((A) over tilde2Delta <-- (X) over tilde (2)Pi(i)) transition at 470.9 nm by laser induced fluorescence (LIF). From the analysis of the relative concentration-time behavior of CCN ((X) over tilde (2)Pi(i)) under pseudo-first-order conditions, the rate constants for the reaction of CCN ((X) over tilde (2)Pi(i)) with a series of normal alkaries (C-1-C-8) were determined for the first time. The new data establish that the gas-phase reactivity of small alkanes (C-1-C-8) towards the CCN radicals follows the linear free energy relationship typical of hydrogen abstraction. A comparison with the corresponding reactions of CN and OH radicals with a series of normal alkanes, leads us to suggest that the reaction of CCN ((X) over tilde (2)Pi(i)) with small normal alkanes proceeds via the mechanism of hydrogen abstraction. The plausibility of the suggested reaction mechanism is strengthened by bond dissociation energy (BDE) correlations and linear free energy correlations.